With the present emphasis on sustainable resources that comes with low environmental impact, corrugated paperboard packaging, in particular using corrugated paperboard is receiving new attention and positive receptions due to its recyclability, relative low cost, good cushioning effects and light weight properties as compared to other packaging materials such as plastic foams, metal and wood containers. The capability of corrugated paperboard to package any tailor-made shapes, sizes and weight has expanded its possibilities to further limits. As a result, there is an increasing interest in utilizing it in protective packaging for various products, e.g. fragile goods such as fresh fruits and vegetables, consumer-packed manufactured products, precise equipments and instruments, industrial machineries, and household appliances, etc. The advantage of corrugated paperboard packaging is enhanced by having its suitability for all different modes of transport, e.g. land, shipping by sea, or by air.
Corrugated paperboard is an environmental-friendly packaging material. It is made of reusable paper and water-based glue, and these materials are recyclable, reusable and biodegradable. The paper based construction material comprises corrugated sandwich structure; a fluted corrugated sheet within several linerboards. The medium as shown in FIG. 1 is the corrugated or fluted paper glued between the linerboard facings. The corrugated paper between facings of corrugated paperboard is called fluting or corrugating medium. The best quality fluting is made from short hardwood fibers of deciduous trees by a special pulp cook method. Such fluting contains only a small percentage of clean, mill waste (kraft). A large part of the fluting mediums, on the other hand is manufactured mainly from waste paper. Flutes that anchored to linerboard with starch based adhesive will enable corrugated paperboard to resist bending and pressure from all directions. When pressured to the side of the board, the space between the flutes acts as a cushion to protect the packaging content. The flutes also serve as an insulator, providing some product protection from sudden temperature changes. Linerboard is the flat facing or liner that adheres to the medium. The outer and inner facings or liners of corrugated board are usually made from the long softwood fibers of coniferous trees which have the desired strength properties. Linerboards can also contain various amounts of recycled or waste paper fibers. Ultimately, vertical linerboard provides additional strength and protects the flutes from damage. Both linerboard and medium are traditionally referred to by their weight, gram per square meter (g/m2).
At the moment, there are several types of combined boards. Firstly, the singleface corrugated paperboard, as shown in FIG. 2 comprises a single liner is applied to one face of corrugated medium, and it is widely utilized as padding or for cushioning. Singlewall, as shown in FIG. 3 comprises two sheets of linerboard, one glued to each side of a fluted medium and is also known as doubleface. Doubleface corrugated paperboards are suited as material for packaging boxes and shipping containers. Whereas, doublewall as shown in FIG. 4 is made up of three sheets of linerboards, with two interleaved and glued corrugated mediums. This grade of paperboard is used mainly for more robust, higher strength containers and for heavy applications, particularly in packaging for export. Triplewall as shown in FIG. 5 is being composed of four flat sheets of linerboard, with three interleaved and glued corrugated mediums. Only few manufacturers make this grade, which is suited for very heavy industrial applications such as semi-bulk commodity bins. Triplewall is recognized as the most layered-combined boards available in the market currently.
The machine used to make these combined paperboards is known as a corrugator. Conventionally, the corrugator is a huge machine that is about 91.44 meters long, 4.5 to 6.1 meters high and 3.7 meters wide. It costs millions of dollars whereby its functions include putting flutes in the medium, glues the medium into linerboard to produce combined boards of singleface as illustrated in FIG. 2, singlewall as illustrated in FIG. 3, doublewall as illustrated in FIG. 4 or triplewall as illustrated in FIG. 5. The combined boards can consist of any combination of liners grades and flute types, namely: A, B, C, E, F, G, K, S. Mill roll stands, or also known as roll stands, hold the giant rolls of linerboard and corrugating material in place. This continuous process begins with reels of linerboard and corrugating medium paper rolls being loaded onto the mill roll stand. As the first paper roll runs out, or as the order is completed, and a different basis weight, width and type must be put in place for the next order, the machine is slowed down and a splicer automatically connects the second paper roll.
The paper is first conditioned with heat and steam and fed between large corrugating rolls, a large cylinder with a corrugated profile which gives the paper its fluted shape in single facer. Starch is applied to the tips of the flutes on one side and the inner liner is glued to the fluting. The corrugating fluting medium with one liner attached to it, which is also known as single face web, travels along the machine towards the double backer where the single face web is bonded to the outer liner and forms the corrugated board. At this stage, different types of combined board, which comprises of continuous sheet as wide as the rolls of container board is traversed through heating or hotplate and cooling sections which ensures the glue bond is strong by gelling the glue and removing moisture. After the board emerges from the double backer it passes through a rotary shear, where it cuts across the whole width of the web. This is used to chop out damage lengths of board. At a slitter scorer machine, a set of rotary knives will slit the paperboard into required width. The scorer will make creasing line, a folding line of paperboard in the machine direction. The slitter knives also trim the outside edges of the paperboard. The board then passes into a numerical control (NC) cutter where the board is cut to the required length. The capability of the corrugator to produce different types of combined paperboards depends solely on only the number of single facer machine fixed on the corrugator. In the conventional corrugating process, there should preferably be one singlefacer machine with three sets of mill roll stands and splicers to produce singlewall paperboard, to produce doublewall paperboard, there should preferably two singlefacers with five sets of roll stands and splicers, for triplewall, there should preferably be three singlefacer machines with seven sets of roll stands and splicers. Most of the corrugator machines available in the market can produce up to doublewall only. There is rarely a corrugating plant that would produce triplewall as they are very expensive.
Unless there are large orders for triplewall using present day methods of production, it is not be feasible to invest millions more on the singlefacer machines, roll stands, splicers as well as the additional machine space in order to produce triplewall paperboards or anything thicker or more robust than them. However due to present day demands and standards within the paper packaging industry itself, there is now a greater need for an even stronger and more robust paperboard, coupled with need for an innovative, cheaper and more economical method of manufacturing multi-layered corrugated paperboard for heavy industrial packaging usage.